This invention relates to a pump, which may be suitable for use as a bladder evacuator or for post-operative flushing of blocked catheters, comprising a nozzle for connection by a tube to a bodily or other cavity and a fluid circulator for imposing on fluid within the tube cyclic changes of pressure to cause the fluid to flow alternately and repeatedly into and out of the cavity thereby to flush the cavity, the circulator and the tube being connected by two different fluid flow paths, namely, an efflux path for flow of fluid away from the cavity into a reservoir of the device and thence to the circulator, and a flushing path for flow of liquid from the circulator to the cavity, each of which paths including a non-return valve whereby, in use of the device, fluid flow is uni-directional, from the circulator through the flushing path to the cavity, and then from the cavity through the efflux path back to the circulator.
Such a pump is useful as a bladder evacuator to generate a fluid flow which serves to carry pieces of bodily tissue from the bladder to the reservoir. It is important that the return flow of fluid from the reservoir to the bladder cavity should not carry back as many tissue pieces as have been swept out of the bladder. Some means of concentrating the tissue pieces in the reservoir is required.
The usual circulator employed with bladder evacuators is a rubber bulb, alternately squeezed and released by the surgeon. Any tissue filter introduced into the flushing path for the purpose of confining tissue pieces to the reservoir should restrict the flow of liquid as little as possible so that the frequency of squeezing and release of the bulb can be as high as the surgeon desires. Further, the surface of the filter should not be such as to become blocked by pieces of tissue.
So far as the present applicant is aware, all attempts previous to the present proposal to meet the above requirements have failed to secure wide acceptance by users. A simple bladder evacuator known by the name "Ellik" continues to be the instrument of choice.
The Ellik device has a shape which resembles that of an hour-glass of which the upper chamber is connected to a rubber bulb and the lower chamber is a collection chamber. Alternate squeezing and release of the bulb, when the device is full of liquid, induces outward and return flow of this liquid along a tube connected to the upper chamber of the device and to the bladder of a patient. Debris and other matter entrained in the return flow is collected in the lower chamber.
It is a problem with the Ellik device that it fails to trap all of the entrained matter in the collection chamber. Instead, some of it remains entrained in the liquid flow and is carried back to the bladder. Some at least of the entrained matter is seen to be "tidal", that is to say, carried backwards and forwards between the bladder and the collection chamber.
Proposals for improvement on the performance of the Ellik device are made in U.S. Pat. Nos. 3,892,226 and 4,282,873 published 1975 and 1981 respectively.
U.S. Pat. No. 3,892,226 to Rosen discloses a bladder evacuator which takes the form of a hand-grippable column divided longitudinally by a web into a downflow channel and an upflow channel. At the foot of the column is a reservoir, and at its head is a nozzle and a pumping bulb. In the web at opposite ends are two non-return flap valves, with the one at the foot of the column seating on an area in which is a plurality of small holes instead of one large one, the small holes serving to block the passage of tissue pieces more effectively than a single large hole.
It is one disadvantage of the Rosen device that the area of the seat of the flap valve at the foot of the column is insufficient for effective filtering. If the holes are usefully small they soon become blocked, but if they are made larger they allow small tissue pieces to pass through. Another disadvantage is that the tissue pieces which are caught on the valve seat are not easily cleaned off, are not included with the reservoir when it is removed from the column to enable its contents to be analysed, and may impede movement of the flap valve member and prevent full closure of the valve.
U.S. Pat. No. 4,282,873 to Roth discloses an evacuator with a nozzle, a pumping bulb and a reservoir in which a quarter turn rotation of the bulb causes an integral stem to rotate within a manifold to close one aperture and open another. A combination of squeezing and releasing the bulb with forward and backward rotation of the bulb achieves the desired uni-directional flow including flow through a filter element carried on the manifold, but the co-ordinated hand movements required to operate the device are found in practice to hinder rapid pumping and deter users.
An earlier proposal is to be found in U.S. Pat. No. 1,925,230 to Buckhout. The device offers the major advantages of a large filter area at a location within its reservoir, and non-return valves spaced from the filter, but it is not a convenient instrument to handle and use and therefore does not find favour with users.
A pumping device is disclosed in GB Patent Application No. 2136690A which is relatively convenient to handle, but it lacks an effective filter or uni-directional liquid flow path and so is not well-suited to achieve the sought-for improvement in filtering performance.